(1) Field of the Invention
This invention relates to shoe machinery and more particularly to a device for properly defining the shape of a shoe upper during a stiffening operation.
(2) Prior Art
Stiffening of portions of shoe uppers by coating the portion to be stiffened with a layer of molten resin and solidifying the resin was disclosed in the U.S. Pat. No. 3,316,573 to Chaplick et al. In the process of that patent, molten thermoplastic polymeric material was spread as a layer on a shoe upper at a temperature at which the thermoplastic material has a viscosity low enough to wet and adhere to the surface of the article to be stiffened but sufficiently high so that it will substantially not penetrate the shoe component, and the layer of material so formed was cooled and shaped to form a stiff, resilient layer holding the article in the desired configuration.
The process referred to has entered into substantial commercial use for the stiffening of toe portions of shoes, but heel portions of shoes because of the relatively small radius curves and the seam, have not lent themselves to deposition of a useful thermoplastic material stiffening layer by procedures shown in the patent.
Stiffening of portions of shoes by disposing them between mating mold halves and injecting molten stiffener material between the shoe upper layers in the mold has been proposed. However, this method has severe economic and operational difficulties which have prevented its acceptance. That is, the special two-part mold is costly particularly since different molds would be required for every distinct style of heel end and in some cases different molds would be required for different sizes of the same style. Further disadvantages are that since molten resin is introduced between two layers of shoe material, dissipation of heat to allow stiffening of the resin is retarded by the heat insulating action of the shoe upper materials so that the "in mold" time is long. Also, the thickness of the resin layer formed is dependent on the space left in the mold between the layer of upper material and the liner and hence varies inversely as the thicknesses of the upper material and liner, which in the case of leather are known to be highly variable even between the two sides of a shoe.
A further procedure for stiffening portions of shoes involves the disposition of a thermosetting material on a stiffener blank or on a portion of the upper by means of a special distributor head. This distributor head squeezes out a pattern of a pasty material from a series of extruder orificii in a plate pressed against the blank or shoe upper and this pattern is spread as a uniform layer by applying pressure to flow the material over the selected area of the shoe component. Because of "stringing" and other problems, this procedure is not suitable for application of molten resinous stiffeners.
Further advances in stiffening of shoe uppers is shown in U.S. Pat. No. 4,344,199 to Bouzianis et al where a reciprocable and rotatable nozzle is disposed on an extruder. A male mold is bolted to a support which in turn is attached to a carrier. Any need to change size or style of a shoe upper being stiffened required unbolting and disassembly of a heavy mold structure from its support. A similar type of mold is shown in U.S. Pat. No. 4,127,910 to Hollick wherein a solid male plug is bolted to a support, and a rubber strip is adhered to the outside; the inner perimeter of which defined a pocket into which the stiffening material would press the inner liner of the shoe upper, after the nozzle had ejected the hot resinous material between the inner liner and the outer layer of the shoe upper prior to its being molded between the male and female mold members, in an attempt to distribute the stiffening resin properly therein.
It is an object of the present invention to provide easily interchangeable, lightweight mold members which can be quickly utilized to minimize machine down-time between shoe size or style changes in a shoe upper stiffening machine.
It is a further object of this invention to provide a mold member capable of providing the proper taper in a stiffening element disposed in the heel pocket of a shoe upper.